1. Field of the Invention
The present invention relates generally to a plate type heat exchanger for two different fluids, and more particularly to a so-called housing-less type automotive heat exchanger or oil cooler usable in combination with an oil filter.
2. Description of the Prior Art
Hitherto it is well known that a variety of plate type heat exchangers have been widely used to cool oil such as lubricating oil in automotive vehicles. Of these, the so-called housing-provided type are extensively used in which a heat exchange element is constructed of a plurality of heat exchange units each formed of two heat transmission plates which are combined, with each other. Oil flows through an oil flowing space defined between the two heat transmission plates. The thus constructed heat exchanger element is disposed within a housing in such a manner as to define a coolant flowing space between the housing inner wall and heat exchange units. Such housing-provided type heat exchanger is complicated in construction and requires many production steps for production of the same, thereby raising production cost of the heat exchanger.
In view of the above, so-called housing-less type heat exchangers have been proposed and put into practical use in order to omit a housing as disclosed, for example, in Japanese Utility Model Publication No. 59-28219. Such a housing-less heat exchanger disclosed in the Publication is constructed of a plurality of heat transmission plates piled up one upon another. Adjacent heat transmission plates are fixed to each other by brazing in order to define an oil flowing space and a water flowing space on the opposite sides of each heat transmission plate. In this housing-less type heat exchanger, each heat transmission plate is formed with oppositely located outwardly projecting sections so that coolant introduction and discharge passages are formed respectively through the projecting sections of each heat transmission plate. Additionally, inlet and outlet pipes are connected to the heat exchanger so as to communicate respectively with the coolant introduction and discharge passages. The water inlet and outlet pipes extend upwardly to supply coolant into and discharge coolant from the heat exchanger. Thus, since the heat exchanger is not provided with a housing, it is simplified in construction and in production is facilitated.
However, the following difficulties have been encountered in such a housing-less type exchanger: Each heat transmission plate is irregular or complicated in profile, and therefore caulking or bending and brazing of the peripheral sections of the adjacent heat transmission plates are difficult, resulting in oil and/or coolant leaking. The heat exchanger is unavoidably provided at its side with two rows of oppositely protruding vertical projections corresponding to the above-mentioned outwardly projecting sections of each heat transmission plate. These vertical projections make it impossible to mount the heat exchanger on an automotive vehicle having limited engine compartment space. Additionally, when mounting an oil filter on the heat exchanger, tools are required to attach the oil filter or detach the same from the heat exchanger, in which the tools unavoidably interfere with the upwardly extending coolant inlet and outlet pipes.